Study of Wavelength Dependence of Plasma Collision Dynamics and Ionization Mechanism in Laser Solid Matter Interactions

该研究项目将提高高功率激光与固体材料相互作用时等离子体碰撞动力学的理解。由于宇宙中超过99.9%的可见物质都处于等离子体状态，因此了解等离子体中粒子电离、电荷碰撞以及光传播和吸收的物理学非常重要。在实验室中产生和研究等离子体的一种方法是使用高功率激光器。 当材料被高功率激光照射时，原子和分子中的束缚电子可以被释放（即，离子化），从而产生等离子体。激光与等离子体的相互作用在材料电离过程中和电离后表现出许多有趣的现象。例如，当被加速的电子与离子碰撞时，通过激光的自由电子加速可以产生高能辐射，例如紫外线和X射线。在这个项目中，将从实验和理论上研究固体中等离子体碰撞动力学的激光波长依赖性。本项目还将通过举办以祖父母为户主的家庭和农村家庭中学生的科学夏令营，促进对传统上在科学方面代表性不足的群体的基础科学教育。由于电子碰撞在等离子体中起着重要作用，因此系统研究电子碰撞频率对于正确理解激光等离子体相互作用至关重要。在本项目中，将通过使用飞秒时间分辨干涉测量法测量电子碰撞时间和等离子体密度，对激光照射下固体中的等离子体动力学进行实验研究。特别是，等离子体动力学上的驱动器波长的效果将被调查。这些实验还将以激光物质相互作用的计算机模拟为基准。这一研究将有助于进一步理解固体中激光与物质相互作用的波长标度。此外，这项研究将影响基于激光等离子体的技术，如激光等离子体加速器，并为使用太瓦和拍瓦峰值功率激光器的高能量密度物理提供指导。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This research project will improve the understanding of plasma collision dynamics when high power lasers interact with solid materials. With more than 99.9% of visible matter in the universe known to be in a plasma state, it is important to understand the physics of particle ionization, charge collision, and light propagation and absorption in a plasma. One method for producing and studying plasma in laboratories is using high power lasers. When materials are irradiated by high power lasers, bound electrons in atoms and molecules can be freed (i.e., ionized) and thus plasma is created. Laser-plasma interactions during and after material ionization exhibit a lot of interesting phenomena. For example, free electron acceleration by lasers can produce high-energy radiation such as ultraviolet and x-ray light when the accelerated electrons collide with ions. In this project, the laser wavelength dependence of the plasma collision dynamics in solids will be experimentally and theoretically investigated. This project will also promote basic science education to groups who have been traditionally underrepresented in science by hosting science camps for grandparent-headed families and for middle school students of rural families.Since electron collision plays an important role in plasmas, systematic studies on the electron collision frequency are critical for understanding the laser plasma interaction correctly. In this project, the plasma dynamics in solids under laser irradiation will be experimentally studied by measuring both electron collision times and plasma densities using femtosecond-time-resolved interferometry. In particular, the effect of the driver wavelength on plasma dynamics will be investigated. The experiments will also be benchmarked against computer simulations of laser matter interactions. This research will significantly contribute to furthering understanding of wavelength scaling of the laser matter interaction in solids. Furthermore, this study will impact laser-plasma-based technology such as laser-plasma accelerators and provide guidance for high energy density physics using terawatt and petawatt peak power lasers.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.